Many motorized wheeled vehicles use one or more clutches to engage and disengage the engine from the transmission when shifting gears. In some cases to control the transfer of torque from the engine to the transmission and/or to the wheels.
One type of commonly used clutch it the multi-plate clutch in which alternating driving and driven plates are compressed together to transmit torque from the engine. To control the activation of such a clutch, a clutch controller typically compares the speed of rotation of the driving plates, which can obtained from the engine for example, to the speed of rotation of the driven plates, which can be obtained from the speed of rotation of a driveshaft connected to one or more wheels for example. By comparing these speeds of rotation, the controller can determine if the clutch is slipping (i.e. the speed of rotation of the driving plates is different from the speed of rotation of the driven plates), or is synchronized (i.e. the speeds of rotation of the driving and driven plates are the same), and can make adjustments accordingly.
While this clutch control method is suitable, since the controller relies on a clutch output (i.e. the speed of rotation of the driven plates) to control the clutch, there is an inherent delay in the controller's response.
Therefore, there is a need for a clutch control method with improved controller response.
The clutch controller usually uses one or more algorithms and/or control maps to control the clutch. These algorithms and maps are based on a desired performance characteristic for the hardware being used, such as the type of clutch. Since the same algorithms and maps are used for multiple vehicles of the same model, in order to keep performance and response levels the same for all these vehicles, manufacturing tolerances need to be small. For example, in order for the clutches being used in the vehicles to provide the same response, when assembling a clutch, once all of the driving and driven plates but one have been assembled, the thickness of the stack of plates is measured, and the last plate is selected from plates of different thicknesses such that once the last plate is assembled, the overall thickness of the stack of plates corresponds to the desired stack thickness. As would be understood, this is time consuming and complicates the manufacturing process of the clutch.
Also, should a user replace a piece of hardware with one which is different from the one originally provided by the original manufacturer, the performance is likely to be affected as the algorithms and maps were not designed for this particular piece of hardware. Examples of this include replacing a clutch with a similar clutch but from an aftermarket manufacturer due to wear or damage of the original clutch, or in the case of a hydraulically actuated clutch, changing the type of fluid used to actuate and/or lubricate the clutch could also affect performance.
Additionally, should the manufacturer want to use the same hardware across different models but provide these models with different performance characteristics, then completely new algorithms and maps need to be developed.
Also, with use, the hardware, such as the clutch, wears down, but the controller does not take into account these changes which can also affect performance.
Therefore, there is a need for a clutch control system which is less sensitive to variations resulting from manufacturing processes, simplifies modifications to be made to the algorithms and maps necessary to take into account changes in desired performance level and hardware, and can take into account normal wear of the components.
Wheeled vehicles having a manual transmission such as some cars typically used normally closed clutches where one or more springs cause compression of the driving and driven plates together. As such, normally closed clutches transmit torque even when no actuation power is provided. Wheeled vehicles having an automatic transmission such as some cars use a torque converter as a device to execute takeoff. As a result, when the car is in gear (i.e. not in neutral), when the driver does not actuate the accelerator pedal and also does not actuate the brake pedal, the car will nonetheless move forward since the torque converter transmits a residual torque to the wheels. This is sometimes referred to as vehicle creep. However, in some types of vehicles, such as motorcycles for example, vehicle creep is not desired. One solution consists in using a normally opened clutch where one or more springs cause the driving and driven plates to be normally spaced apart. Although this eliminates creep, it causes a lag in the actuation of the clutch when the driver needs torque to be transmitted to the wheels.
Therefore, there is a need for a clutch control method which reduces the above-mentioned lag resulting from the use of a normally opened clutch.
Finally, in hydraulically actuated clutches the pressure of the hydraulic fluid supplied to the clutch determines if the driving and driven clutch plates are slipping relative to one another or are synchronized. However, for a given method of controlling the clutch's hydraulic fluid supply system, different hydraulic fluid viscosities will result in different hydraulic fluid pressures being supplied to the clutch, thus resulting in different performances. One of the factors affecting hydraulic fluid viscosity is the temperature of the hydraulic fluid.
Therefore, there is a need for method of controlling a clutch which accounts for variations in temperature of the hydraulic fluid.